MEMS Piezoelectric (Voltage vs. Eigenfreq)

Hi,

I am changing the voltage across the piezoelectric beam actuator I've created. I expect to see a different set of eigenfrequency numbers when I change the voltage. However, the numbers remain the same.

Under solve parameters
Analysis Types: Piezo Solid (smpz3d) Eigenfrequency with Eigenfrequency Solver.

I'm reading the eigenfrequency numbers from
Point evaluation > Solution to use > eigenfrequency

Any ideas??

-Albert